A vehicle may include an internal combustion engine to propel the vehicle and the engine may include a turbocharger to increase output of the engine. The turbocharger may be driven via exhaust gases to pressurize air entering the engine, thereby increasing the engine's capacity to produce power. The turbocharger may also include an electric machine to increase air flow to the engine during times when engine exhaust flow is low. The electric machine may be supplied power from an inverter. The inverter converts direct current (DC) power to alternating current (AC) power so that the electric machine may generate torque to rotate the turbocharger's compressor. The inverter may include power filtering capacitors that have to be charged to a threshold level before the electric machine may be operated as a motor. The power filtering capacitors may be supplied with power from a vehicle system power supply via a power contactor. The vehicle system power supply may not be available to supply power to the power filtering capacitors for a period of time due to diagnostics, system checking functions, and other reasons at a time of an engine start request. Therefore, the power contactor may be held in an open state for a period of time before the power filtering capacitors may be charged. As a result, it may not be possible for the electric machine to supply torque to rotate the turbocharger compressor for a predetermined amount of time after the engine is started and running. Consequently, if the vehicle is started and a driver requests power just after the engine is started, engine performance may be less than is expected.
The inventors herein have recognized the above-mentioned issues and have developed an engine operating method, comprising: receiving input to a controller indicative of a request to start an engine; and operating an electric turbocharger in a generator mode and charging a power filter capacitor coupled to a DC bus via the controller in response to the received input.
By operating the electric turbocharger in a generator mode and charging a power filter capacitor that is coupled to a DC bus in response to input to a controller that is indicative of an engine start request, it may be possible to provide the technical result of charging the power filter capacitor before the electrical power contactor is closed so that the electric turbocharger may be operated in a motor mode earlier as compared to if the power filter capacitor is charged solely via a vehicle system power supply.
The present description may provide several advantages. In particular, the approach may reduce an amount of time between when a power contactor is closed and when an electric turbocharger may be operated in a motor mode. Further, the approach may decrease an electrical load on a vehicle system power supply. In addition, the approach may provide precise charging control for power filter capacitors.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.